Without Humans, How the World Would Have Been?

The natural diversity of large mammals is shown as it would appear without the impact of modern man (Homo sapiens). The figure shows the variation in the number of large mammals (45 kg or larger) that would have occurred per 100 x 100 kilometer grid cell. The numbers on the scale indicate the number of species.CREDIT: Illustration: Soren Faurby

Without humans, the whole world would have looked like Serengeti, says a new study that projected a scenario of the natural worldwide diversity patterns of mammals in the absence of past and present humans.

Since the greatest diversity of large mammals is found in Africa, which reflects past human activities – and not climatic or other environmental constraints, the new study presents what the world map of mammals would look like if modern man (Homo sapiens) had never existed.

In a world without humans, most of northern Europe would probably now be home to not only wolves, Eurasian elk (moose) and bears, but also animals such as elephants and rhinoceroses, it says.

The current diversity of large mammals is shown. It can clearly be seen that large numbers of species virtually only occurs in Africa, and that there are generally far fewer species throughout the world than there could have been.CREDIT: Illustration: Soren Faurby.

In their new study, researchers from Aarhus University, Denmark have shown in their analysis that the mass extinction of large mammals during the Last Ice Age and in subsequent millennia is largely explainable from the expansion of modern man (Homo sapiens) across the world.

In the follow-up study, they investigated what the natural worldwide diversity patterns of mammals would be like in the absence of past and present human impacts, based on estimates of the natural distribution of each species according to its ecology, biogeography and the current natural environmental template. They provide the first estimate of how the mammal diversity world map would have appeared without the impact of modern man.

“Northern Europe is far from the only place in which humans have reduced the diversity of mammals – it’s a worldwide phenomenon. And, in most places, there’s a very large deficit in mammal diversity relative to what it would naturally have been”, says Professor Jens-Christian Svenning, Department of Bioscience, Aarhus University, who is one of the researchers.

Africa is the last refuge because “the continent is one of the only places where human activities have not yet wiped out most of the large animals,” says Postdoctoral Fellow Soren Faurby, Department of Bioscience, Aarhus University, who is the lead author on the study.

The study has been published in the journal Diversity and Distributions.